There are really only 5 players that would make sense in that kind of a deal.

Harden - This would be wild. Can't think that KD wants to be paired with James again after he bailed on Brooklyn. Also, don't think Philly would have any interest in Ayton coming back with Embiid on the roster.
Irving - This would be wild. Can't think that KD wants to be paired with Kyrie again after he bailed on Brooklyn. Part 2.
Porzingis - Maybe this makes sense. Porzingis fits what the Suns would want to do, and in a vacuum is better than Ayton.
FVV - Don't think I would do this. FVV isn't all that much better than CP3, and takes volume away from Durant and Booker.
Middleton - Basketball wise this should work. Middleton fits the timeline and has the right fit with Durant and Booker. Would Milwaukee want Ayton back?

I guess they could target a player under contract, but then what else do they have to pay to legitimately upgrade on Ayton.